1. Field of the Invention
The present invention relates to a session initiation protocol (SIP)-based session service, and more particularly, to a method of securing a respondent's privacy in an automatic answer mode of a push-to (PT) service and to any PT client terminal and/or server for implementing the method.
2. Discussion of the Related Art
A SIP is a signaling protocol prescribing procedures for allowing terminals to identify opposite terminals to communicate with and to find out locations thereof and for allowing the terminals to create, delete, and change multimedia service sessions. A SIP-based service has a request/response structure for controlling the establishment, correction, and release of the multimedia service session. The SIP-based service employs SIP URLs (Uniform Resource Locator) similar to e-mail addresses to identify users and thus provides services without dependence on IP (Internet Protocol) addresses.
An example of the SIP-based session service is a Push-To (PT) service. The PT service has been developed for providing fast communications between providers and users through mobile communication networks and generally includes such communication services wherein, among clients having set a session through a server, one client having a right of talk or a right of transmission assigned thereto transmits media data including voices or images and the other clients participating in the session receive the media data. The PT service includes a PoC (Push-to-talk Over Cellular) service of providing a call service to transmit voice data, a PTV (Push-To Video) service of transmitting image or video data, and a PTD (Push-To Data) service for transmitting various data. Voices, images, and data can be transmitted to one receiver (1-to-1) or a receiver group (1-to-many) such as in a group chat session.
In the PT service supporting a 1-to-1 communication and a group communication, individual privacies should be secured at the time of communication. More specifically, when the PT service is used, each user can select depending on his own intention whether his identity such as his nickname and/or his IP address should be open (not private) or anonymous (private). The individual intention on the publication of the user's identity (i.e., the identify of the user who has been invited to participate in a PT session) may be included as privacy information in a response message responding to a session invitation, which is then transmitted to the opposite party.
For example, the privacy information can be included in a header portion of a message 200 OK, which is a response message to a session invitation message, as a privacy header, and can be transmitted to an inviting PT server. The inviting PT server publishes or hides the identity of a respondent (invited PT user) to or from the inviting PT user on the basis of the privacy information included in the received response message. When the privacy information is not included in the received response message, the inviting PT server considers that the respondent (invited PT user) agrees to the publication of his identity to the inviting PT user or other PT users in the PT session.
However, in such a privacy securing method of the PT service according to the related art, the privacy of the respondent (invited PT user) might not be secured properly when the procedure is performed in an automatic answer mode. In the automatic answer mode, an automatic response message (e.g., a 183 SESSION PROGRESS message) not including the privacy information can be often transmitted “directly” to the inviting PT server through the invited PT server. Here, the term “directly” means that the automatic response message from the invited PT user is transmitted to the inviting PT server, regardless of the fact whether a response message (e.g., a message 200 OK) is received from the invited PT user having received a session invitation message. As a result, the inviting PT server does not receive or have the privacy information of the invited PT user in the automatic answer mode, and the identity of the invited PT user is made known to the inviting PT user (and maybe to other PT users) against the invited PT user's intention of keeping his identity private, which is a problem.